1. Field of the Invention
The invention relates to a method for producing a layer structure comprising a smoothed interlayer and an overlying layer applied on the interlayer. Layer structures of this type are produced for example as substrates for electronic, optoelectronic and microelectromechanical applications. The layers are for example deposited on a carrier by means of CVD methods or connected to the carrier by means of bonding methods. Representatives of such substrates are, for example, semiconductor wafers with a plurality of deposited or bonded layers, in particular SOI substrates (silicon on insulator), substrates with a layer of SixGe1-x (silicon-germanium) and a layer of strained silicon (strained silicon on bulk) and sSOI substrates (strained silicon on insulator).
2. Background Art
The application of the overlying layer to the interlayer constitutes a critical step because it necessarily requires the microroughness of the interlayer to be as low as possible. Various methods have been proposed, therefore, in order to meet this requirement. Thus, in accordance with US2005/0104067 an SGOI substrate (SiGe on insulator) is subjected to chemical mechanical polishing prior to the deposition of a layer of strained silicon, in order to achieve the necessary smoothing. In accordance with US2003/0060020, polishing is effected using a magnetorheological fluid (MRF) in order to reduce the microroughness further. What is disadvantageous about these methods is the outlay which they require. U.S. Pat. No. 6,995,077 describes a method which serves especially for smoothing semiconductor wafers composed of monocrystalline silicon prior to the deposition of an epitaxial layer, and comprises a treatment of the semiconductor wafer with a mixture of hydrogen and hydrogen chloride.